The class of polymers of carbon monoxide and olefin(s) has been known for some time. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical initiators, e.g., peroxy compounds. U.K. No. 1,081,304 produced similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium as catalyst. Nozaki extended the reaction to produce linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. See, for example, U.S. Pat. Nos. 3,914,391, 3,835,123 and 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon has become of greater interest in part because of the greater availability of the polymers. The more recent processes for the production of these polymers, now becoming known as polyketones or polyketone polymers, are illustrated by a number of published European Patent Applications including 121,965, 181,014, 213,671 and 257,663. The process, now considered to be broadly conventional, generally involves the use of a catalyst composition formed from a compound of a Group VIII metal selected from palladium, cobalt or nickel, the anion of a non-hydrohalogenic acid having a pKa below about 6 and preferably below 2, and a bidentate ligand of phosphorus, arsenic or antimony. The resulting polyketone polymers are relatively high molecular weight thermoplastics having established utility in the production of shaped articles by the methods which are conventional for thermoplastic polymers.
The process of producing the polyketone polymers typically involves contacting the carbon monoxide and ethylene hydrocarbon(s) under polymerization conditions in the presence of the catalyst composition and a reaction diluent in which the catalyst composition is soluble but in which the polyketone polymer product is relatively insoluble. Then the polymer is partially cleaned up in additional process steps, such as those described in U.S. Pat. No. 4,798,884, having a common assignee. The working-up process claimed in the patent No. '884 is a process for working up a linear alternating copolymer of carbon monoxide and ethylene which process comprises washing the copolymer with an organic solvent selected from the group consisting of aliphatic alcohols, ketones, ethers, nitriles and saturated hydrocarbons, separating the copolymer from the solvent and drying the copolymer at a temperature of at least (T-30).degree. C., wherein T is the boiling point of the solvent at room pressure, in the absence of molecular oxygen and in the absence of water.
A new process variation has been discovered which results in the preparation of polymers having improved stability.